Upright vacuum cleaners and power heads for canister vacuum cleaners in all of their designs and permutations have become increasingly popular over the years. Upright vacuum cleaners generally incorporate a nozzle assembly which rides on wheels over the floor surface to be cleaned. A canister assembly is pivotally mounted to the nozzle assembly. The canister assembly includes an operating handle that is manipulated by the user to move the vacuum cleaner back and forth across the floor. The canister assembly also includes either a bag-like filter or a cyclonic separation chamber and filter combination that traps dirt and debris while substantially clean air is exhausted by a fan that is driven by an onboard electric motor. It is this fan and motor arrangement that generates the drop in air pressure necessary to provide the desired cleaning action. In most upright vacuum cleaners sold today, a rotary agitator is also provided in the nozzle assembly. The rotary agitator includes tufts of bristles, brushes, beater bars or the like to beat dirt and debris from the nap of a carpet being cleaned while the pressure drop or vacuum is used to force air entrained with this dirt and debris into the nozzle of the vacuum cleaner.
Power heads generally include a nozzle opening, a rotary agitator in the nozzle opening and a motor for driving the rotary agitator through a drive transmission system. In either an upright vacuum cleaner/extractor nozzle or a power head assembly, as the single agitator rotates and engages the surface being cleaned, it has a tendency to pull or push forward or backward depending upon its direction of rotation. At certain times and under certain operating conditions, this imparted motion becomes a hindrance to the user's effective operation and directing of the upright vacuum cleaner/extractor or power head and impedes its ease of operation. In order to address this shortcoming, the present invention relates to a power head or upright vacuum cleaner/extractor incorporating twin agitators that may be made counter-rotating. In this way the net pulling and pushing effect of each agitator is effectively canceled to significantly ease manipulation of the power head or vacuum cleaner/extractor by the user. Additionally, the present invention relates to a unique, novel and efficient drive system for the twin agitators.